Hormones mediate environmental effects on physiology and behavior and affect development, reproduction, stress, and aging and may also be involved in learning and memory processes. Effects of hormones on brain function and behavior can be transitional by activating physiological changes only during the presence of a hormone. Or they can be permanent by organizing anatomical structures and their properties, in particular during early development, resulting in irreversible changes of brain function and behavior. There is a need for a greater diversity of animal models to better understand when and how these effects take place and to test various hypothesis that have been proposed. This proposal describes field and laboratory experiments with birds which address: 1) Mechanisms of environmental, hormonal and neural control of food caching behavior and associated spatial memory of black-capped chickadees. 2) Effects of maternally inherited hormones on the development of the behavior and brain function of offspring and the evolutionary significance of such a mechanism. Hormone assays, field observations of behavior, behavioral testing under controlled conditions, hormonal manipulations, and anatomical studies will be used to probe these questions. The possible involvement of the avian hippocampus in stress and food caching may offer new opportunities for studying how hormones that regulate stress also influence learning and memory. The hippocampus of food caching birds seems ideal material for studying these cross-roads between hormones, stress and learning. Finally, the presence of variable amounts of maternally inherited hormones during early development may be a mechanism that causes non-genetic variability in brain function and behavior. These studies may provide one more way of understanding the contributions of the mother and the environment to each new generation.